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But in exchange for that long-overdue swim-friendliness, other features are lost. There's no heart rate tracking, and it doesn't have a display. Are you OK with that compromise?

The Flex 2 looks, in many ways, like the perfect slim tracker from Fitbit that we'd wanted for a while: It's like Fitbit's version of the Jawbone Up2. It's $100 (£80 or AU$130 converted) and will begin shipping in early October. It comes with a rubber strap in both large and small sizes, but the beauty of the Flex 2 is its customization.

You can pop out the tracker and pop it into a different color wristband, a metal bangle or even a necklace. It's the most versatile Fitbit, and much like the older Flex, it comes with a variety of fashion-branded accessories from Tory Burch and others. It's an overdue upgrade, and the water resistance and swim racking on the Flex 2 might be reason enough to get it for some.

I do like the Flex 2. It's the tracker to get if you want something that can be both discreet and stylish. It's a sleeker tracker than the bulkier Fitbit Alta released earlier this year. It's priced well. But yes, there are sacrifices to be made.

Swim-proof (finally!)

The Flex 2 is the first Fitbit you can wear in the shower and while swimming. It's waterproof down to 50 meters (about 165 feet) and can be used in both fresh water and salt water. I love not having to take the tracker off when it's time to shower, which also means I'm less likely to forget it on my dresser.

Like the Charge 2, the Flex 2 can also automatically recognize and record workouts. This includes walking, running, biking, aerobic exercise and others. Due to the new swim-proof design, it's also the only Fitbit that can track swimming (you have to enable the feature in the Exercise section of the app) Now that Fitbits are effectively automatic trackers, it's a little easier to swallow the fact that this doesn't have a display.

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It's all about accessories

The Flex 2 is 30 percent smaller than its predecessor, the Fitbit Flex. It's slim and discreet, which is what appeals to me, and it could even be worn next to a traditional watch (if you have the wrist room). My only complaint is with the strap. It's secure and never fell off my wrist, but you have to swap out the two-prong connector when switching to a new strap, which was actually pretty difficult.

Besides the two different-sized bands in the box, there are a variety of accessory straps in multiple colors and designs. There are rubber ones, leather ones (coming in 2017 from the designer collections), and gold and silver bangles and pendants. The accessories start at $15 (£10, AU$20) for rubber straps, all the way to $100 (£75, AU$130) for the gold bangle.

A quick poll of my female colleagues found that these designs, mainly the pendant, were appealing, especially compared with the nearest fitness-accessory equivalent, the Misfit Shine necklace (pictured above). One colleague complained that the bangle was "lacking pizzazz" and another said the Fitbit pendant was a little "too long," but both liked these options better than the rubber strap.

Everyone agreed that having these accessory options is a good thing. They help keep the Flex 2's design fresh, and help it not feel like a fitness tracker. While some complained about them being too expensive, most agreed they would make nice gifts.

In addition to the bangles and pendants mentioned above, Fitbit said we can expect more luxurious bands from designers Tory Burch, Vera Wang and Public School.